Environmental Risk Assessment for Shale Gas DOE Research.pdf · Environmental Risk Assessment for Shale…

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  • Environmental Risk Assessment for Shale Gas Development

    Daniel J. Soeder, NETL, Morgantown, WV

    Presentation for Chesapeake Bay Program STAC

    State College, PA, April 11, 2012

  • 2

    Concepts of Risk

    Risk = probability x consequences

  • 3

    Risk in Engineered Geologic Systems

    Threat: external events that cause risk

    Threats can exploit vulnerabilities

    Threats are assessed in terms of probability (Precautionary Principle)

    Vulnerability: internal weakness that invites risk

    Vulnerability only exists in the face of a threat

    Vulnerability is assessed in terms of likely threats (Calculated Risk)

    Both threats and vulnerabilities must be assessed to

    properly understand risk.

    Risk can vary over time >>

    (CO2 injection example)

  • 4

    NETL Office of Research and Development

    New program charge in 2011 for

    EPAct projects: Assess risk from oil

    and gas production

    Program Technical Areas:

    Ultra-Deep Offshore/Frontier

    Regions

    Unconventional Resources,

    primarily shale gas

    Focus Areas for Risk Assessment:

    Potential impacts from hydraulic

    fracturing

    Potential impacts from poor

    wellbore integrity

    Potential impacts to water quality

    Potential impacts to air quality

  • 5

    Potential Shale Gas Risks

    Engineering Risk Assessment:

    What is the probability of a contaminant release?

    What is the probability of an induced seismic event?

    What risks are short term versus long term?

    What are the receptors?

    Air, water, landscapes, ecosystems/habitat

    The major unknown risk is cumulative effects

    How will multiple wells make an impact?

    What is threshold for impacts? (i.e. impervious surfaces)

    Risk reduction through regulations and enforcement

    Not all known environmental impacts are regulated

    Not all regulations are fully enforced

  • 6

    Risk Assessment in Engineered Systems

    DOE National Risk Assessment Partnership (NRAP) Cooperative effort among NETL, LBNL, LLNL, LANL, and PNNL

    Scenario-based, site modeling for carbon storage in engineered

    geologic systems

    Sometimes called site performance assessment

    Uses FEP-based scenarios and probabilities Feature: property of a geologic system that may affect risk

    Event: an action that introduces higher risk conditions into a system

    Process: a method or procedure that increases risk

    Predict performance of components using high fidelity

    models

    Run scenarios to validate models/reduce uncertainty

    Provide quantitative basis for geologic storage security

  • 7

    Integrated Risk Assessment Models

    Integrated Assessment Models (IAM) Probabalistic assessment of system risk (multi-site)

    Interaction of sites can increase or decrease risk

    Divide system into components, develop detailed,

    validated models, reduce uncertainty

    Develop reduced order models (ROM) to reproduce

    detailed model predictions of components

    Integrate ROMs through IAM to predict total system

    performance, interactions and risk

    Calibrate using field data and databases

    Quantify potential long-term liability

    Risk Profile Risk Management Validation

    (Quantify) (Strategy) (Field Data)

  • 8

    Adapting NRAP to Shale Gas

    Components: old wells with

    potential casing and cement

    integrity issues, watered-out

    reservoirs

    Design Basis: greatest risk

    is immediately after injection;

    when pressure is highest.

    Model: seal integrity, well

    bore leakage, migration

    through intermediate strata,

    changes in pressure and

    saturation

    Validation: monitoring,

    verification and accounting

    Components: new wells,

    with new fractures, tight, dry,

    overpressured reservoir

    Design Basis: greatest risk

    is after frac during early

    stages of production under

    initial high pressure.

    Model: fracture heights,

    fresh groundwater depth,

    bypass flowpaths, wellbore

    leakage, pressure/stress

    changes

    Validation: field monitoring

    and analyses (need defining)

  • 9

    Risk Assessment via Incident Reports One method to help determine the components of an IAM is to

    review past incident data at oil and gas production sites.

    Reporting only the number of incidents is meaningless: Discharge of industrial waste can range from a spilled quart of motor oil to a leak from a ten thousand

    gallon frac fluid tank.

    Classification of incidents:

    Administrative: missing signage, poor record-keeping, incorrect permit application or

    other missing or wrong "paperwork."

    Minor: small spills or leaks that require clean up, but are contained on site, do not

    enter the groundwater, and can be remediated by the local rig crew.

    Significant: larger spills or leaks that could potentially leave the site but did not, and

    required outside assistance (i.e. HAZMAT team) to help clean up.

    Serious: explosion, fire, stream contamination or fish kill, human injury or fatality,

    significant property damage, contamination of a drinking water supply.

    Catastrophic: destruction of site and serious damage to surrounding area.

    Frequency, type and seriousness of incidents over time help define

    risk trends.

    State regulatory agencies are the source of most incident reports.

  • 10

    Water Contamination Incidents Kell, Scott, 2011, State Oil and Gas Agency Groundwater

    Investigations and their Role in Advancing Regulatory Reforms: A Two-

    State Review: Ohio and Texas, Groundwater Protection Council, 165

    p., August 2011, Oklahoma City, OK:

    Incident: "any detected contamination of groundwater or disrupted water

    supply due to development of oil and gas or management of wastes."

    Ohio reported 144 incidents in 33,304 wells between 1983 and 2007

    (rate = 0.432%); no significant shale gas production at the time.

    Most Ohio incidents occurred during drilling/production operations

    85 of the 144 incidents (60%) occurred between 1983 and 1988 (boom).

    Texas reported 211 incidents in 187,788 wells between 1993 and

    2008 (rate = 0.112%); Barnett Shale play began in 1997.

    Most Texas incidents occurred during waste disposal

    Texas RR Commission "witnesses" drilling and completion operations on

    about 1/3 of wellsites

    Both states reported zero incidents over the time periods studied

    associated with well stimulation (hydraulic fracturing)

  • 11

    Water Resource Risks/Questions Supply

    3 to 4 million gallons per well

    2/3 to 3/4 consumptive use

    Watershed management vs. stress

    Watershed Impacts Stream degradation from roads-pads-operations

    Water quality degradation from leaks/spills

    Groundwater Infiltration from above

    Frac fluid/formation water from below

    Changes in GW flow directions or gradients

    Fate of fluids that remain underground

    Water quality Infiltration of chemicals/spills into shallow

    groundwater

    Long-term leaching of drill cuttings

    Minerals-sediment-gas contaminating nearby water wells

    http://pubs.usgs.gov/fs/2009/3032/

  • 12

    Hydraulic Fracture Heights and Aquifers

    0

    1000

    2000

    3000

    4000

    5000

    6000

    7000

    8000

    9000

    1 51 101 151 201 251 301 351

    Dep

    th (

    ft)

    Frac stages (sorted on Perf Midpoint)

    Marcellus Mapped Frac Treatments

    fracTOP

    perfTOP

    Perf Midpoint

    perfBTM

    fracBTM Microseismic data, plotted against deepest freshwater aquifer on a county by county basis.

    Reference: Fisher, Kevin, 2010, Data confirm safety of well fracturing, The American Oil and Gas Reporter, July 2010, www.aogr.com

    http://www.aogr.com/

  • 13

    Surface Leaks and Spills

    Higher risk to groundwater and surface

    water than frac fluid underground (Groat,

    UT Austin study, 2012)

    Baseline data on existing contaminants are

    required to assess drilling impacts.

    Studies underway in 2012:

    Retrospective investigation of impacted

    streams; large and small watersheds

    Comparison of stream reaches: affected

    and unaffected; also compare two similar

    small watersheds (WVU)

    Comparison of impacts versus watershed

    management practices (Pitt)

    Assessment of impacts, damage, costs

    Forensics of what caused the leak

    Better leak detection and warning, including

    field-deployable instruments to monitor

    surrogates (pH, conductance, turbidity)

    Prospective data from Marcellus Test Site

    Photo by Doug Mazer, used with permission.

  • 14

    Geochemistry of Shale Drill Cuttings Vertical: 5 metric tons of cuttings

    Horizontal: 270 metric tons of cuttings

    Anoxic black shales preserved organic

    material with associated radionuclides.

    Highest gas content is in the organic-rich,

    radioactive black shale; cuttings at surface

    are exposed to air and rainwater

    Oxidized forms of these metals are much

    more soluble and mobile

    TimeofFlight Secondary Ion Mass Spectrometry (TOFSIMS) to determi

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